Selenium photoelectric cells are well known and commonly consist of a layer of polycrystaline selenium deposited on one surface of an iron substrate plate. The selenium surface away from the plate (the top surface) receives a contact such as a conductive disk which serves as a first electrode while the iron plate substrate acts as the other electrode. The selenium surface is photosensitive and, when illuminated, will generate a potential between its two electrodes which can be used as a voltage source for electrical loads including meter loads. Selenium is also known to exhibit a marked change in resistance when exposed to light, and this resistance change can also be used for metering purposes.
It is also known that the electrode connected to the selenium surface can be a fluid, particularly, a liquid. Thus, U.S. Pat. No. 1,375,474 in the name of W. O. Snelling, issued Apr. 19, 1921 discloses a selenium based photo-electric apparatus in which a transparent electrode formed of a gelatine or starch paste or an aqueous salt solution or a dilute acid contacts the selenium surface. Other gels and oils are suggested as an electrode. Snelling also discloses a metal grid for making contact to the fluid electrode.
It is very difficult to form a grid electrode and to contact it without accidentally short circuiting the electrode to the iron plate substrate by puncturing the thin selenium layer. Further, only a limited output power can be produced with the electrode fluids proposed in the prior art.
It would therefore be very desirable to produce a selenium photoelectric device using a fluid electrode which can be easily and reliably contacted by an output lead and it would be desirable to employ a fluid which would produce an increased output electrical power from the cell.